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Modification of antiphase domain sizes in omphacite by dislocation glide and creep mechanisms and its petrological consequences

Published online by Cambridge University Press:  05 July 2018

H. L. M. van Roermund
Affiliation:
Ecole Normale Supérieure de Lyon, Lab. des Sciences de la Terre, 46 Allée d'Italie, 69364 Lyon Cedex 07, France
J. M. Lardeaux
Affiliation:
Ecole Normale Supérieure de Lyon, Lab. des Sciences de la Terre, 46 Allée d'Italie, 69364 Lyon Cedex 07, France

Abstract

A T.E.M. study of omphacites from the western Italian Alps (Sesia Lanzo Zone and Monviso eclogites) has revealed a bimodal size distribution of antiphase domains: (a) 250–350 Å, (b) ≥ 2500 Å. In addition observed dislocation substructures and ‘large-scale’ antiphase domains are intimately interconnected.

A model is presented that can explain modification of the antiphase domain sizes by the interplay of cooling/growth and dislocation glide and/or creep mechanisms. Subsequent coarsening of the modified antiphase domains is inferred to be the result of surface free-energy processes. The model clearly illustrates that only the ‘relatively undeformed’ areas containing the small-scale antiphase domains can be used for thermometric methods.

Type
Research Article
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1991

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Footnotes

*

Present address: Laboratoirc de Pétrologie Métamorphique, C.N.R.S., URA 736, Université de Paris 7, 4 Place Jussieu, F-75252 Paris Cedex 05, France.

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